This project is aimed at studying the molecular architecture of gap junctions in an attempt to establish a more precise structure-function correlation. A portion of the project is concerned with the changes occurring in the structure of gap junctions after treatments which result in uncoupling of adjacent cells for small ions. Structural differences between coupled and uncoupled junctions were seen in both invertebrate (crayfish ganglia) and vertebrate (rat stomach and liver) systems. The changes associated with functional uncoupling are characterized by a tighter and more regular pattern of aggregation of the junctional intramembrane particles and a possible decrease in particle size. In the crayfish a decrease in junctional thickness was also observed. In another line of study attempts have been made to isolate intramembrane particles (connexons) from enriched gap junction fractions. Gap junctions were isolated by treating rat liver plasmamembrane fractions with the detergent Sarkosyl NL-97 in the absence or presence of EDTA. In the absence of EDTA the junctions were well preserved, while in the presence of EDTA they were highly damaged displaying large connexon-free areas, fragmentation and membrane separations. In addition many connexons were freed from the junctions and were seen as independent units on the carbon grid. A detailed study of the architecture of free connexons has allowed the drawing of a tentative model which depicts them as cylinders made of six radially arranged subunits shaped as dumbbells. Present work is involved in the isolation of pure fractions of connexons and in the definition of their chemical composition.